The present invention relates to a process for converting olefinically unsaturated compounds directly to their corresponding diols or polyols in the presence of a specifically defined oxidation catalyst composition, water, and an oxygen containing gas.
It is well known from the technical literature, that olefins can be oxidized to their corresponding diols, stoichiometrically or catalytically with osmium oxide compounds, particularly osmium tetroxide.
The non-catalytic, i.e. stoichiometric, cis-hydroxylation of alkenes with OsO.sub.4 has been conventionally characterized as taking place via the formation, with the alkene, of an osmium (VI) intermediate ester complex. (For a recent review, see, "Osmium Tetroxide Cis Hydroxylation of Unsaturated Substrates", by M. Schroder, Chem. Rev. Vol 80, pp. 187-213 (1980) hereinafter Schroder).
To convert the non-catalytically prepared osmium (VI) ester complex intermediate to the diol, the intermediate can be hydrolyzed reductively. Reductive hydrolysis is conventionally carried out by using alkali metal sulfites, bisulfites, lithium aluminum hydride, or hydrogen sulfide to yield the corresponding cis-diols together with lower valence forms of osmium which are removed by filtration.
It has been observed by Criegee (see Schroder, page 191, Col. 1 11-12) that for non-catalytic cis hydroxylation of alkenes, the rate of formation of the Osmium (VI) ester complex is greatly increased in the presence of tertiary amines such as pyridine. This rate enhancement is believed to occur via the formation of some type of amine Osmium (VI) ester complex (see Schroder page 191, Col. 2). However, enhancement of the rate of the Osmium (VI) ester complex does not necessarily result in an enhancement of the overall hydroxylation rate, since the rate of hydrolysis of the ester complex must also be considered. In this regard, it has been noted that whereas certain osmium ester complexes and amine ester complexes (e.g. with pyridine) can be hydrolyzed reductively, amine ester complexes are more resistant to such hydrolysis. (See Schroder page 191, Col. 2, last paragraph; and page 193, Col. 1, first paragraph).
In contrast to the stoichiometric non-catalytic mode of cis hydroxylation with OsO.sub.4, the catalytic mode employs a secondary oxidant to oxidatively hydrolyze the intermediate Osmium (VI) ester and regenerate the OsO.sub.4 which can undergo further reduction by the substrate olefin. A variety of oxidants have been employed in conjunction with OsO.sub.4 such as H.sub.2 O.sub.2, t-butylhydroperoxide and oxygen.
The use of oxygen as an oxidant has encountered considerable difficulty due to the appreciable overoxidation of the products, particularly at elevated temperatures (e.g. 70.degree.-80.degree. C.), leading to the formation of keto or acid products. However, if the reaction temperature is lowered to reduce overoxidation, the reaction rate is so low that yields of cis-diol are drastically reduced. An additional disadvantage of the use of oxygen oxidant is that the reaction is highly pH dependent (see Schroder, page 210, Col. 1).
The poor performance of oxygen based osmium catalyzed olefin hydroxylation systems is unfortunate, since such systems have inherent advantages over organic hydroperoxide based systems. For example, hydroxylation systems employing organohydroperoxide oxidants result in the conversion of the organohydroperoxide to its corresponding alcohol during the formation of the desired olefin derived diol. Thus, for example, t-butylhydroperoxide is converted to t-butylalcohol. The commercial attractiveness of such processes is dependent on the ability to use or sell the organic alcohol co-product in addition to the diol. Given the fluctuation in economic conditions, however, it may be difficult to dispose of large quantities of these organic alcohol co-products in an economically attractive manner. In any event, it can be troublesome, when the quantity of one product, selected on the basis of marketing possibilities for a given period, necessarily determines the quantity of some other product which may be smaller or larger than desirable in view of changing marketing requirements within that same period. It can, therefore, under certain circumstances be considered as a disadvantage of the aforenoted organohydroperoxide based processes that such large quantities of organic alcohols are formed as co-products, even though under other circumstances the formation of two products may well be found acceptable.
In contrast, oxygen based hydroxylation systems do not produce an oxidant derived alcohol co-product that must be disposed of, which can be a significant advantage.
The search has, therefore, continued for ways of improving the rate and/or selectivity of osmium catalyzed oxygen based processes for hydroxylating olefins.
One step in this direction, is disclosed in commonly assigned U.S. Pat. No. 4,390,739 by R. Austin and R. Michaelson. This patent describes a process for the hydroxylation of olefins using oxygen as an oxidant, a catalytically active metal oxide catalyst such as OsO.sub.4, and at least one transition metal salt co-catalyst such as copper bromide. This process can also be conducted in the optional presence of a second co-catalyst such as alkali metal halides. Pyridine is disclosed as a suitable solvent for this process but no mention is made of any promoting effect being associated with this solvent medium. While the use of the transition metal co-catalyst substantially improves the reaction rate and/or selectivity of the hydroxylation reaction, a further improvement in this process is still being sought.
U.S. patent application Ser. No. 310,217, filed Oct. 9, 1981, now abandoned, of common assignee herein by R. Michaelson and R. Austin discloses the use of various osmium halide and oxyhalide catalysts in the presence or absence of a wide variety of co-catalysts and an oxidant selected from hydrogen peroxide, organohydroperoxides, or oxygen. Pyridine is disclosed as a suitable buffer for pH control in this application, which pH control is required when employing hydrogen peroxide.
Commonly assigned U.S. Pat. No. 4,314,088 and a continuation-in-part thereof, namely, U.S. Pat. No. 4,393,253 by R. Austin and R. Michaelson collectively, disclose the use of various halide containing co-catalysts in conjunction with osmium tetroxide catalyst and organohydroperoxide oxidants to hydroxylate olefins. The halide containing co-catalysts include alkali and alkaline earth metal halides, hydrogenhalides, quaternary hydrocarbyl phosphonium halides, halogens, and transition metal halides.
U.S. patent application Ser. No. 399,270 filed July 19, 1982, by R. Austin and R. Michaelson is directed to a process for hydroxylating olefins in the presence of an organohydroperoxide oxidant, an osmium containing catalyst and an organic halogenated hydrocarbon co-catalyst.
Commonly assigned U.S. patent application Ser. No. 394,414, filed July 1, 1982 by R. Michaelson and R. Austin, is directed to the use of carboxylate salts as co-catalysts for use in conjunction with osmium oxides as a catalyst and organohydroperoxide as oxidant to hydroxylate olefins.
Commonly assigned allowed U.S. patent application Ser. No. 397,997 filed July 14, 1982, now U.S. Pat. No. 4,413,151, by R. Michaelson, R. Austin, and D. White is directed to a process for hydroxylating olefins in the presence of a supported osmium containing catalyst, optional co-catalysts (e.g. CuBr.sub.3) and an oxidant selected from hydrogen peroxide, organohydroperoxides and oxygen.
Commonly assigned U.S. patent application Ser. No. 420,137 filed Sept. 20, 1982 by R. Michaelson, R. Austin and D. White is directed to a process for hydroxylating olefins in the presence of an osmium carbonyl catalyst optional co-catalysts and an oxidant selected from hydrogen peroxide, organohydroperoxide, and oxygen.
Commonly assigned U.S. patent application Ser. No. 440,964, filed Nov. 12, 1982 by R. Michaelson, R. Austin, and D. White is directed to a process for hydroxylating olefins in the presence of an osmium oxide catalyst, optional co-catalysts and sodium hydroxide as a promoter.
While all of the above described commonly assigned patents or patent applications disclose the use of pyridine as one of many suitable solvents, none of these applications show or suggest either alone or collectively, that any promoting effect can be obtained from pyridine when employed in accordance with the presently claimed invention.
Moreover, to the best of the inventors' knowledge, not a single prior art publication shows the use of any tertiary amine as a promoter to enhance the overall rate of osmium catalyzed cis-hydroxylation of olefins with oxygen. While catalytic cis-hydroxylation of tetra and tri-substituted alkenes with t-butylhydroperoxide and OsO.sub.4 has apparently been conducted in the presence of pyridine, the oxidative hydrolysis of such esters has been found to be particularly slow due to steric considerations (see, Schroder, page 193, Col. 2, first paragraph).
Notwithstanding the above, the following discussion is intended to provide a background of osmium based olefin hydroxylation processes.
U.S. Pat. No. 3,335,174, is directed to the use of Group Vb, VI-b and VII metal halides and oxyhalides (e.g., OsCl.sub.3) as hydroxylation and esterification catalysts in conjunction with aqueous H.sub.2 O.sub.2 as an oxidant. However, the process for using this catalyst requires the presence of lower aliphatic hydrocarbon acids such as glacial, formic, acetic and propionic acid as solvents. Under these conditions the reaction times vary from 1/2 to 4 hours, but at the shorter reaction times it is disclosed that substantial amounts of epoxide result thereby indicating that the reaction proceeds via the peracid route. The only yield disclosed is obtained in connection with tungsten hexachloride in Example 1. This yield is extremely low, i.e. 22%, and includes both half-acetate and diol. When an equivalent of Example 2 of this patent was conducted, the conversion of hydrogen peroxide was found to be 10%, the selectivity to diol was 10%, the selectivity to diacetate was 20% and the diol yield was 1%. Thus, among the major disadvantages of the process described in this patent are the low selectivities to diol and the corrosiveness of metal halides in the presence of glacial acids such as acetic acid.
Japanese Patent Application No. Sho 54-145604, published Nov. 14, 1979, is directed to a process for hydroxylating olefins in the presence of OsO.sub.4, a quaternary ammonium salt such as tetraethylammonium bromide, and a peroxide including organoperoxides and H.sub.2 O.sub.2 as the oxidant. The use of oxygen as the oxidant is not disclosed nor is the co-presence of co-catalyst I salts as described herein disclosed. Selectivities to glycol of from about 4.5 to about 66% are disclosed. H.sub.2 O.sub.2 oxidant in combination with OsO.sub.4 is known as Milas reagent which can lead to non-selective oxidation of olefins as well as over oxidation. H.sub.2 O.sub.2 is also substantially more expensive than oxygen or air. Accordingly, the uses of organohydroperoxides as well as H.sub.2 O.sub.2 as oxidants are each associated with their own disadvantages.
U.S. Pat. No. 2,214,385 discloses the use of hydrogen peroxide and a catalytically active oxide, such as osmium tetroxide, dissolved in an essentially anhydrous, non-alkaline, inert, preferably organic, solvent, to convert, by oxidation, unsaturated organic compounds to useful oxygenated products such as glycols, phenols, aldehydes, ketones, quinones and organic acids. The formation of glycols is achieved by conducting the reaction at temperatures of between several degrees below 0.degree. C. and 21.degree. C. Such low reaction temperatures drastically and disadvantageously, reduce the reaction rate to commercially unacceptable levels. At temperatures greater than 21.degree. C., the formation of aldehydes, ketones, and acids is favored.
U.S. Pat. No. 2,773,101 discloses a method for recovering an osmium containing catalyst such as osmium tetroxide, by converting it to the non-volatile osmium dioxide form, distilling the hydroxylation product, reoxidizing the osmium dioxide to the volatile osmium tetroxide, and then recovering the same by distillation. Suitable oxidizing agents used to re-oxidize the osmium dioxide, include inorganic peroxides such as hydrogen peroxide, sodium peroxide, barium peroxide; organic peroxides, such as t-butyl peroxide or hydroperoxide, benzoyl peroxide; as well as other well known oxidizing agents such as oxygen, perchlorates, nitric acid, chlorine water and the like. As with other methods of the prior art, the above process yields undesirable by-products (see Col. 1, line 55) thus reducing the selectivity of the process.
British Patent Specification No. 1,028,940 is directed to a process for regenerating osmium tetroxide from reduced osmium oxides by treatment of the latter with molecular oxygen in an aqueous alkaline solution. More specifically, it is disclosed that when osmium tetroxide is used by itself as an oxidizing agent, or as a catalyst in conjunction with other oxidizing agents, to oxidize hydrocarbons the osmium tetroxide becomes reduced, and in its reduced form is less active than osmium tetroxide itself. Consequently, by conducting the oxidation reaction in the presence of an alkaline medium and supplying oxygen to the medium throughout the process, the osmium tetroxide is maintained in a high state of activity. The oxidation products disclosed include not only ethylene glycol from ethylene but also organic acids from such compounds as vicinal glycols, olefins, ketones, and alcohols. While the pH of the alkaline medium is disclosed broadly for all possible reactions as varying from 7.5 to 12 for purposes of re-oxidizing reduced osmium tetroxide, the pH employed in the example for preparing ethylene glycol is 9.5. If the pH is too high, a wide variety of products are produced as a result of over oxidation and/or degradation. Thus, the sensitivity of the process to the pH of the medium necessitates rigid pH control which is economically disadvantageous.
U.S. Pat. No. 4,255,596 is directed to a process for preparing ethylene glycol in a homogeneous single-phase reaction medium using ethylbenzene hydroperoxide as the oxidizing agent dissolved in ethylbenzene and osmium tetroxide as the catalyst. The pH of the reaction medium is maintained at about 14 by the presence of tetraalkyl ammonium hydroxide. A small amount of water can dissolve beneficially in the medium to reduce by-product formation and improve selectivity to the glycol.
U.S. Pat. No. 4,049,724 describes the preparation of glycols from alkenes and from unsaturated alcohols in an aqueous system using osmium tetroxide and specifying stable and water-soluble aliphatic hydroperoxides, such as tert-butyl hydroperoxide, while a critical pH of 8 to 12 is maintained by a suitable combination of alkali metal buffering compounds. The preparation of propylene glycol utilizing tert-butyl hydroperoxide is exemplified in the patent at a selectivity based on the hydroperoxide of 45 percent.
None of the aforenoted patents disclose the osmium containing-co-catalytic system described herein.
See also: U.S. Pat. No. 3,317,592 (production of acids and glycols using oxygen as oxidant, OsO.sub.4 as catalyst at pH 8-10); U.S. Pat. No. 3,488,394 (discloses hydroxylation of olefins by reacting olefin and hypochlorite in the presence of OsO.sub.4); U.S. Pat. No. 3,486,478 (discloses reaction of hypochlorite and olefin in an aqueous medium and in the presence of OsO.sub.4 catalyst to hydroxylate the olefin); U.S. Pat. No. 3,928,473 (hydroxylation of olefins to glycols with O.sub.2 oxidant, octavalent osmium catalyst (e.g., OsO.sub.4), and borates as promoter); U.S. Pat. No. 3,931,342 (discloses a process for recovering glycols from an aqueous solution containing alkali metal borate and osmium compounds (e.g., OsO.sub.4); U.S. Pat. No. 3,953,305 (discloses use of OsO.sub.4 catalyst for hydroxylating olefins which is regenerated by oxidizing hexavalent osmium with hexavalent chromium and electrochemically regenerating hexavalent chromium); U.S. Pat. No. 4,203,926 (discloses ethylbenzene hydroperoxide as oxidant used in two phase system to hydroxylate olefins in presence of OsO.sub.4 and cesium, rubidium and potassium hydroxides); U.S. Pat. No. 4,217,291 (discloses the oxidation of Osmium (III) or (IV) in an ionic complex with oxygen and an alkali metal, ammonium, or tetra (-lower) alkyl ammonium cation to a valency of greater than +5+organo hydroperoxides); and U.S. Pat. No. 4,229,601 (discloses the use of cesium, rubidium and potassium hydroxides as promoters for OsO.sub.4 catalyst and t-butyl hydroperoxide oxidant for hydroxylating olefins).